A tonneau cover system uses a unique and novel way to control the movement of a side cover. The system utilizes a drum that is coupled to the side cover and a cable which is coupled to the drum. Movement of the cable causes the side cover to move between open and closed positions. The cable can be coupled to a retractable roof. Movement of the retractable roof between raised and stowed positions causes the side cover of the tonneau cover system to move between its open and closed positions.